A simpler picture of satellite chlorophyll fluorescence

The Fluorescence Line Height (FLH) algorithm provides a standard method of measuring solar-stimulated chlorophyll fluorescence from coastal and ocean waters using the Moderate Resolution Imaging Spectroradiometer (MODIS), the Medium Resolution Imaging Spectrometer (MERIS) or other satellite sensors having the necessary spectral bands near 680 nm. In many coastal areas, this can provide superior estimates of chlorophyll concentration when compared to estimates derived from the standard green/blue algorithms. However, at least one significant data supplier normalizes the derived FLH values (to Normalized Fluorescence Line Height) on the assumption that the fluorescence signal is proportional to local solar irradiance. This is not the case, and normalization results in errors which make the fluorescence data much less useful. This paper demonstrates that FLH should be used as a measure of chlorophyll concentration without normalization.